Fluid-operated electric switch



July i967 D. A, DURRAN ETAL 3,330,929

FLUID-OPERATED ELECTRIC SWITCH Filed Sept 9, 1966 INVENTORS JO/wila fl. .oz/flew WHll/s e, @,Pggow y BY #a7 @Ma United States Patent O 3,330,929 FLUID-OPERATED ELECTRIC SWITCH Donald A. Durran, Manhattan Beach, and Wallis R. Grabowsky, San Pedro, Calif., assignors to the United States of America as represented by the Secretary of the Air Force Filed Sept. 9, 1966, Ser. No. 579,186 4 Claims. (Cl. 200-152) This invention relates generally to a high current electric switch, and more particularly to a huid-operated electric switch capable of carrying high current and provides sequential switching for two related circuit components.

There are presently available many mechanical-operating electric switches with high current capacities, but they are usually of semi-manual operation and do not make or maintain good electrical contact. On the other hand, there are a variety of jitter-free electronic switches, but these have a relatively low current capacity.

The present invention provides a huid-operated electric switch which can carry large currents, of the order of 50,000 amperes, and operates in a much shorter time period than previous mechanical-operated electric switches.

It is an object of the present invention to provide an improved high current switch capable of closing an electrical circuit and closing another portion of that circuit a predetermined time later.

Further features and the method of operation of the present invention, together with other objects, will become apparent in the following description considered in conjunction with the accompanying drawing of which:

FIG. 1 is a cross-sectional view of the switch of the present invention which is connected to a magnetic field inductance coil and a capacitor bank, and

FIG. 2 is a perspective detailed view of a part in FIG. 1.

One of the applications of the novel switch of the present invention is to connect a fully charged capacitor bank across a low inductance magnetic field coil in order to build a high intensity magnetic iield and then crowbar the coil. The description of the operation of the present invention is given in connection with this particular use for illustration purposes only. The use of the switch of the present invention is not limited to the application described herein.

In FIG. l, capacitor 1 represents the above mentioned capacitor bank and inductance coil 2 represents one or more magnetic iield coils. Switch 3, as shown in FIG. 1, incorporates the novel features of the present invention. As will be explained hereinafter, switch 3 when actuated causes the stored charge on capacitor 1 to energize coil 2.

Referring to FIG. l, switch 3 is housed in a metallic cylindrical shell 4, which is open at both ends. At one end of shell 4 is the driver gas inlet 5, which consists of a small opening around its entire periphery. A collar 6 encloses inlet -to form a high pressure chamber. The driving gas is forced into this high pressure chamber from a gas source (not shown) when valve system '7 is opened.

Switching is accomplished by two reservoirs of mercury liquid 8 and 9, which are carried in annular piston 10. FIG. 2 shows more clearly annular piston 10, which is constructed with an electrical insulating material. Mercury is selected in this instance as a matter of convenience. It is appreciated that other conducting iiuids may be employed where such is adaptable to the needs of the particular switch. The reference to the uid conducting medium or mercury is meant to include all such mediums in this description.

ICC

Splash guard 11 is provided above upper reservoir 8 so that the mercury liquid is somewhat constrained in a conducting geometry during piston deceleration.

Grooves 12 and 13, as shown in FIG. 2, are placed in piston 10 for the placement of O-rings. Two similar grooves (not shown) are provided on the inside of piston 10. In FIG. l, there is shown O-rings 14-17 placed within these grooves.

In order to cushion piston 10 at both ends of the stroke, there are installed bumpers 18 and 19, which are made of rubber or a similar type resilient material.

Centrally disposed in shell 4 is a solid metallic disc 20. Extending from each end of disc 20 are metallic rods 21 and 22.

Rods 21 and 22 are held in place and electrically insulated from piston 10 and shell 4 by insulators 23 and 24, respectively.

Nut 35 is threadably engaged at the end of rod 21 to securely close that end of the switch 3. At the other end of switch 3, metallic cylinder 25 is mounted around insulator 24, as shown in FIG. 1. Insulating plug 26 iits snugly between cylinder 25 and shell 4 to seal oit that end of switch 3.

Bus bar 29 (partly shown) is mechanically coupled and electrically connected to metallic cylinder 25 by means of being vised between nuts 27 and 28. Similarly, bus bar 32 (shown in part only) is vised between nuts 30 and 31, which electrically connect bar 32 to conductive rod 22. Washer 33 which is made of a nonconductive material insulates but bar 32 from metallic cylinder 25 and bus bar 29.

Valve system 34 introduces hydrogen above piston 10 and splash guard 11 to suppress arcing at the contacts. The hydrogen gas also serves to return piston 10 to the bottom of the stroke. Valve system 34 is not part of the y claimed invention. By mounting switch 3 vertically, piston 10 would return to the bottom of the stroke by the force of gravity and valve system 34 could be eliminated.

Bus bars 29 and 32 mechanically and electrically connect switch 3 to a capacitor bank, represented as capacitor 1 in FIG. 1. Capacitor bank 1 is charged by an exterior power supply (not shown).

The manner of operation of switch 3 will now be eX- plained. After capacitor bank 1 is fully charged, valve 7 is opened introducing a gas into collar 6 to drive piston 10 upwards. As the gas pressure accelerates piston 10, lower puddle of mercury 9 makes contact with conductor 20. At this time capacitor bank 1 is connected across inductance coil 2 and capacitor bank 1 discharges into inductance coil 2. The discharge path is from the top terminal of capacitor 1, through bus bar 32, down conductors 22 and 20, through mercury liquid 9 and the bottom portion of shell 4, and into the terminal of coil 2 that is connected to collar 6.

Piston 1li continues to move upwards and a predetermined time later the upper puddle of mercury 8 makes contact with cylindrical conductor 25. The spacing of the two mercury reservoirs 8 and 9 and contacts 20 and 25 is selected so that lower reservoir 9 remains electrically connected to contact 20 after reservoir 8 contacts cylinder 25. When mercury reservoir S initially contacts cylinder 25, both capacitor bank 1 and inductance coil 2 are shorted out. The shorting path for capacitor 1 is from bus bar 32, through conductors 22 and 20, through mercury 9, along shell 4 between the two mercury reservoirs, through mercury 8 to cylinder 25, and along bus bar 29. The shorting path for inductance coil 2 is from bus bar 29, along cylinder 25, through mercury 8 to shell 4, and along shell 4 to collar 6.

At the time when mercury reservoir 8 makes contact with cylinder 25, the current in coil 2 reaches its peak positive value. By providing a short circuit across coil 2 when its peak value is reached, it is possible to maintain the peak iield intensity for a relatively long period of time, which is determined by the L/R decay of coil 2. The short circuit path across coil 2 allows the passage of current stored within coil 2 without applying a signilicant reversal of voltage across capacitor bank 1, where such a voltage reversal could injure the capacitor bank.

Valve system 34 furnishes hydrogen above piston 19 and mercury reservoirs 8 and 9 to suppress arcing at the contacts.

To reset switch 3 for the next cycle, the driving gas is vented from below piston 1() through a valve located in collar 6 (not shown) and the compressed hydrogen above piston 10 returns it to the bottom of the stroke.

We claim:

1. An electrical switch comprising a metallic cylindrical shell, a piston member positioned within said shell, said piston having a first and second electrical contact section separated by an electrical insulating material, said lirst contact section being adjacent the resting position of said piston, means for driving said piston from said resting position at one end of said shell towards its other end, means for returning said piston to its resting position, a iirst stationary electrical contact connected to said shell, second and third stationary electrical contacts positioned within but electrically insulated from said shell, said second lstationary contact touching said piston and located between said first and second contact sections when said piston is in its resting position, said third stationary contact located above said piston in said resting position and rubbing against said second contact section as said piston is driven, the distance between said irst and second contact sections and between `said second and third stationary contacts being such -that as said piston is driven said iirst contact section iirst touches said second stationary contact and as the piston continues to move said second contact section touches said third stationary contact, said first and second contact sections remaining, respectively, in electrical contact with said second and third stationary contacts until said piston reaches the end of its forward stroke.

2. The electrical switch of claim 1 wherein said first and second contact sections vconsists of mercury reservoirs.

3. An electric switch comprising a metallic cylindrical shell, said shell being closed at one end with an electrical insulating plug, a hollow-centered piston positioned within said shell, said piston having first and second electrical contact sections separated by an electrical insulating member, said piston normally resting adjacent to said electrical insulating plug, said first contact 'section being closer to said electrical insulating plug than said second contact section, means for driving said piston from said resting position towards the other end of said piston being located between lsaid piston in its resting position and said insulating plug, a metallic disc positioned within said hollow-centered piston between said first and second contact sections and in rubbing contact with the side of said piston as it moves past said disc, a metallic rod secured to one side of said disc and extending in the opposite direction of said resting position out the end of said shell, a cylindrical insulating member covering said rod and having two sections, the lirst section extending from the end of said shell along said rod for a short distance and having an outer diameter smaller than the diameter of said disc, the second section extending between l,the side of said disc and the end of said rst section and having a diameter equal to said disc diameter, a metallic collar fitting 'snugly around said iirst section and along its entire length, said collar having an outer diameter equal to said disc diameter, a second electrical insulating plug fitting between said collar and said shell to close the end of said shell, means for returning said piston t0 said resting position being located below said insulating plug, a rst electrical terminal connected to said collar, a second electrical terminal connected to said rod, a third electrical terminal connected to the outside of said shell, the distance between said rst and second contact section and between said disc and collar being such that as said piston is driven forward said iirst contact section initially contacts said disc and as said piston continues to move said second contact section cornes in contact with said collar while said irst section continues electrical contact Y with said disc and for the remainder of the forward stroke said tirst contact section remains in electrical contact with said disc and said second contact section remains in electrical contact with said collar.

4. The switch as described in claim 3 wherein said g iirst and second electrical contact sections consist of mercury reservoirs. 

1. AN ELECTRICAL SWITCH COMPRISING A METALLIC CYLINDRICAL SHELL, A PISTON MEMBER POSITIONED WITHIN SAID SHELL, SAID PISTON HAVING A FIRST AND SECOND ELECTRICAL CONTACT SECTION SEPARATED BY AN ELECTRICAL INSULATING MATERIAL, SAID FIRST CONTACT SECTION BEING ADJACENT THE RESTING POSITION OF SAID PISTON, MEANS FOR DRIVING SAID PISTON FROM SAID RESTING POSITION AT ONE END OF SAID SHELL TOWARDS ITS OTHER END, MEANS FOR RETURNING SAID PISTON TO ITS RESTING POSITION, A FIRST STATIONARY ELECTRICAL CONTACTS SAID SHELL, SECOND AND THIRD STATIONARY ELECTRICAL CONTACTS POSITIONED WITHIN BUT ELECTRICALLY INSULATED FROM SAID SHELL, SAID SECOND STATIONARY CONTACT TOUCHING SAID PISTON AND LOCATED BETWEEN SAID FIRST AND SECOND CONTACT SECTIONS WHEN SAID PISTON IS IN ITS RESTING POSITION, SAID THIRD STATIONARY CONTACT LOCATED ABOVE SAID PISTON IN SAID RESTING POSITION AND RUBBING AGAINST SAID SECOND CONTACT SECTION AS SAID PISTON IS DRIVEN, THE DISTANCE BETWEEN SAID 